[Letux-kernel] Audio Offset for handsfree speakers

aTc atc at k-n-p.org
Tue Dec 28 21:49:48 CET 2021


Should have posted this a few days ago, but reading through the docs 
about the trim/offset functionality gives me the feeling that it's not 
actually some hardware after the DAC adjusting the voltage, but an 
offset applied by the driver/ABE to the audio data before sending it off 
to the DAC, as part of the the normal processing it does (or doesn't in 
our case with the broken driver)

from the audio spec pdf :

"
The HS channels must be enabled by the following sequence to minimize 
click and pop:
1. Application companion reads offset data through I2C or PDM interface 
(register HSOTrim in Table 4-44)
2. Application companion subtracts offset from audio data
(between interpolation filter and digital modulator)
3. Application companion send ICN data through PDM interface
"

Which would explain why I'm not really seeing/hearing any changes.


On 12/14/21 15:07, H. Nikolaus Schaller wrote:
> HI,
> 
> 
>> Am 14.12.2021 um 15:00 schrieb aTc <atc at k-n-p.org>:
>>
>> On 12/14/21 12:36, H. Nikolaus Schaller wrote:
>>> Hi aTc,
>>> that is nice!
>>> Where can I find the patches? I think they should go into 5.10.y, 5.15.y and 5.16 as well.
>>
>> This is just a quick hack to see if changing the offset registers actually makes a difference. It just shows the value as unsigned, instead of the positive/negative offset it should probably show.
>> I'll have a look around for a more proper way to implement it, if you think this functionality is worth having in the mixer.
> 
> Indeed. Just let me know if there is something to test or merge...


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